The FAST Is Wrong, Bob

What happens when you routinely do an unnecessary test that rarely changes management? Essentially, nothing.

So, here is a randomized, controlled trial demonstrating precisely that.

This trial looks at the Focused Assessment with Sonography in Trauma exam, as performed in pediatric blunt trauma patients. The FAST, if you recall, is generally indicated primarily for hypotensive blunt trauma patients – that is, it has supplanted diagnostic peritoneal lavage as a non-invasive alternative. It does not routinely provide a diagnosis, but it helps guide initial management and may triage a patient to emergency laparotomy rather than resuscitation and further testing.  Therefore, in a stable pediatric trauma patient, the pretest likelihood of a significant finding – free fluid relating to hemorrhage from trauma – is quite low. Furthermore, because many significant intra-abdominal injuries to solid and hollow organs are missed by ultrasound, a negative FAST has poor negative likelihood ratios and should not substantial affect decisions for advanced imaging as otherwise clinically indicated.

So, then, this trial is a bit of an odd duck with respect to any expected difference observed – and that’s precisely what they found in their “coprimary outcomes”. Among the 925 patients randomized to trauma team assessment alone or trauma team assessment supplemented by Emergency Physician FAST, there was no significant difference in imaging, Emergency Department length of stay, missed intra-abdominal injuries, or total hospital charges. The authors hypothesized, based on adult data, there might be savings at least in ED LOS – though, I might rather suggest adding in one more non-diagnostic test to the acute evaluation is more likely to mildly prolong LOS.

There are also issues generalizing this study setting, where ~53% of patients in each cohort received CTs, to other institutions. Interestingly, mean time to CT was over 2 1/2 hours, suggesting a great deal of observation and reassessment drove imaging decisions rather than the initial evaluation. Then, after expert review, EPs incorrectly identified a positive FAST in 10 out of 23 cases – and missed 11 true positives, as well.  The FAST, even at this academic medical center where it is done as routine, cannot be relied upon.

The sum of this evidence is: no change in practice. A stable patient is, by definition, stable for imaging as indicated – and the FAST is an unnecessary part of the initial clinical evaluation.

“Effect of Abdominal Ultrasound on Clinical Care, Outcomes, and Resource Use Among Children With Blunt Torso Trauma”